Most pre built bikes have the steer tube cut to the maximum recommended height. If you need the bars higher, you flip the stem, it that isn't hight enough, either you should be looking at a frame with a higher head tube or you change to a stem with more rise. If you need the stem lower, you move spacers from below to above the stem. Once you get the fit dialled in, it is up to you whether you cut the steer tube or not